The invention relates to an arrangement for contactless inductive transmission of electrical power.
An arrangement of this type is known from the application WO 92/17929 A1. This application describes an inductive energy-distribution system that inductively transmits electrical energy to one or a plurality of movable consumers via a double line.
Ferrite bodies 2 are moved between these double lines l.sub.1 and l.sub.1 ' (FIG. 1B); these bodies support a secondary winding w.sub.2 that supplies the energy to drives and consumers on the moved systems. The ferrite bodies having the secondary windings are referred to hereinafter as transmitter heads. The conductors l.sub.1 and l.sub.1 ' of the double line (FIGS. 1B and 2) are secured to conductor supports S1 and S1' comprising magnetically and electrically non-conducting material. The double line is surrounded by an E-shaped ferrite core 2, whose center leg MS projects deep into the space between the conductors and supports the secondary winding w.sub.2, by way of which energy is tapped and supplied to the moved consumer. The inductive energy-transfer arrangement known from this publication comprises, in the simplest case, a middle-frequency generator, which feeds an elongated conductor loop formed by the conductors l.sub.1 and l.sub.1 ' with a high-frequency current; the two conductors form a double line.
FIGS. 1B and 2 show this type of double line of the related art, with a plan and cross-sectional view of a movable transmitter head 1 comprising an E-shaped ferrite core 2 having the secondary winding w.sub.2 on its center leg MS. A relatively high frequency, at least 10 kHz, is required to keep the transmitter head or heads as small as possible.
Arrangements having elongated conductors are referred to as line conductor or line pole systems, because the magnetic alternating flux extending transversely to the direction of movement is always directed uniformly along the conductor, and thus forms linear poles. In double lines, the moved transmitter head comprises at most an E-shaped ferrite core that surrounds the two stator conductors and conducts the magnetic flux through the secondary winding.
Energy transmissions of this type have numerous applications in areas in which conventional loop lines or trailing cables are advantageously replaced. For example, a transmission with loop contacts is associated with spark formation, wear and noise. Significant applications for contactless transmission of electrical energy are in the traveling cranes of hoists, high-lift storage or magnetic paths. This type of system would also be advantageous for energy transmission into elevator cars. Robots that must travel a specific path to work at different locations can likewise be supplied with energy by such a system.
In an arrangement according to FIGS. 1A and 1B, the middle-frequency generator MFG feeds the current I, at a frequency above 10 kHz, into the conductor loop formed by l.sub.1 and l.sub.1 '. This conductor loop generates scatter fields, which are indicated by .PHI..sub.c and .PHI..sub.c ' in FIG. 1.
Moreover, the double line comprising l.sub.1 and l.sub.1 ' is covered by an aluminum housing 7 in the front part of the conductor loop. Covers are basically necessary to prevent further propagation of the scatter field .PHI..sub.c, because it causes disturbances in adjacent signal-current circuits, for example, and influences the electromagnetic compatibility. With high powers, the danger of harm to human health may arise.
In the rear part of FIG. 1B, the indicated scatter fluxes .PHI..sub.O and .PHI..sub.O ' indicate that the field scatters significantly further into the surroundings without a cover housing.
The greatest disadvantage of this arrangement is the high inductance of the double line comprising the conductors l.sub.1, l.sub.1 '. In addition to the unhindered propagation of the scatter fields in unshielded double lines, the relatively large spacing D between the conductors l.sub.1 and l.sub.1 ' is the primary cause of the high inductance. This spacing D must, however, have a minimum value so that the center leg MS of the E-core supporting the secondary winding w.sub.2 can be guided between the conductors l.sub.1 and l.sub.1 '. The space requirement of the center leg and the secondary winding, and thus the spacing D, is determined by the power to be transmitted.
At the high transmission frequencies, the power inductances cause high inductive voltage drops that must be compensated through a large outlay for capacitors.
Elektrie 34, 1980, Volume 7, discloses an arrangement for inductive energy transmission to hauling locomotives. This arrangement employs double lines laid on the roof of a mine tunnel. Ferrite bodies 2 that support a secondary winding w.sub.2 move between these double lines l.sub.1, l.sub.1 ' (FIG. 1B); the winding supplies the energy to drives and consumers on the moved systems. The ferrite bodies with the secondary windings are referred to hereinafter as transmitter heads.
The above publication describes methods of compensating the inductive voltage drop on the lines and at the scatter inductances of the transmitter heads through capacitors switched in series with the double line and the secondary windings. The energy can be transmitted to at least two movable consumers by way of the same double line.
The inductance of the double lines has a decisive effect on the possible length of the travel path of the moved systems. For many applications, the arrangement is very costly, because it requires an additional cover housing 7 along with the double line. To prevent loss of current, the conductors l.sub.1 and l.sub.1 ' of the double line must comprise a high-frequency litz produced from individually-insulated conductors, which is standard in high-frequency technology.